Panel of plastic material, and process and device for its fabrication

Abstract: The invention relates to a panel of plastic material which consists of two sheets (1, 2) of thermoplastic material (polypropylene) filled with wood flour or similar (known as Wood-Stock), the two sheets (1, 2) having delimited areas of mutual contact (202) which are distributed in any way, are of any shapes and sizes, and are surrounded at least partially by cavity areas (3) in which the said two sheets (1, 2) are separate from each other; the cavity areas (3) may or may not communicate with each other, and the thickness of each of the two sheets (1, 2) is from 0.3 to 1.2 mm. The invention also relates to a process of fabricating the said panel and a device for the application of the process.

Description: The invention relates to a panel of plastic material. Panels of plastic material are very widely used at present in various branches of industry, for example in the inner facing of vehicles, in building, in furniture manufacture, and other areas. The object of the invention is to provide a facing panel of the type indicated above, in such a way that its weight can be reduced by simple and easily formed construction, while improving its qualities of flexibility, rigidity and strength. The invention achieves the said object with a panel of the type described initially which consists of two sheets known under the registered trademark Wood-Stock, in other words a thermoplastic material (polypropylene) filled with wood flour or similar, these two sheets having delimited areas of mutual contact which are distributed in any way, are of any shapes and sizes, and are surrounded at least partially by cavity areas in which the said two sheets are separate from each other; the cavity areas may or may not communicate with each other. Each of the sheets of Wood-Stock has, in particular, a thickness from 0.3 to 1.2 mm, preferably from 0.5 to 0.6 mm. The outer side of the sheet on the visible face of the panel, and optionally also the outer side of the sheet on the rear face of the panel, may be covered with a finishing sheet, such as a cloth, a fabric, a non-woven fabric, simulated leather, adhesive melamine papers, or similar. The finishing sheets, particularly non-woven fabrics, may have weights from 20 g/m 2 to 500 g/m 2 . In one possible and preferred composition, the sheet consists of polyester, viscose, polypropylene, nylon, cotton mixture, PVC, melamine material, or similar. In one embodiment, one of the sheets of Wood-Stock is substantially flat, or is shaped in a form complementary to the surface to which it is to be applied or adapted, or has a substantially continuous development according to the shape required by the client, while the other is further shaped so that it has a plurality of indentations in the areas of contact with the first sheet. The sheet provided with indentations may form the visible face or the rear face of the panel, as necessary. In an alternative embodiment, both sheets of Wood-Stock may have a plurality of indentations forming the areas of mutual contact. Owing to this construction, the weight of the panel according to the invention may be reduced by between approximately 10% and 60% by comparison with Wood-Stock panels of conventional construction, with a consequent saving of materials and costs. The particular structure of the panel provides it with considerable flexibility while considerably increasing its strength. Despite the reduction of weight by comparison with the conventional solutions, the panel maintains its characteristics of rigidity. This particular construction also enables the load-bearing section to be varied as necessary and thus to make the most critical areas stronger. The invention also relates to a method of fabricating the said panels, comprising the following stages: heating the Wood-Stock sheets; feeding the lower sheet to the lower part of a press; inserting at least one or more blowing nozzles so that they are disposed above the outer edge of the lower sheet of Wood-Stock; feeding the second sheet of Wood-Stock to a position of superimposition on the first lower sheet of Wood-Stock, so that the second sheet is disposed over the end of the blowing nozzle; partially compressing the two sheets of Wood-Stock against each other along their outer edges, to provide a substantially hermetic joint between the sheets of Wood-Stock along the outer edges; blowing air between the sheets by means of the blowing nozzle or nozzles, and closing the upper press part against the lower press part. According to an improvement, the outer finishing layer or layers of the sheets of Wood-Stock may be applied to them beforehand, for example during the stage of extrusion of the sheets. The device for the fabrication of the panel according to the method described above comprises a heating oven followed by a forming press consisting of two parts which can be compressed against each other, preferably while in the lower press part there are provided removable means of compressing the two sheets of Wood-Stock against each other along their outer edges. The method and device described above for the fabrication of the panel according to the invention may be used to form panels having either intercommunicating cavities or separate cavities, in a simple, relatively rapid way, while limiting the air requirement and the number of blowing nozzles. The invention also relates to other characteristics which further improve the panel and the method and device for its fabrication as described above, which form the subject of the subsidiary claims. The particular characteristics of the invention and the advantages derived therefrom will be understood in greater detail from the description of some preferred embodiments, illustrated by way of example and without restriction in the attached drawings, in which Fig. 1 is a perspective view of a panel according to the invention; Fig. 2 is an installation for the fabrication of the panel according to Fig. 1; Fig. 3 is a transverse section through the press in the open position; Fig. 4 is a transverse section through the press in the closed position; Fig. 5 is a plan view of the lower press part for the application of a method of fabricating the sheet according to a variant embodiment; Figs. 6 to 9 are transverse sections through the press for fabricating the panel according to the invention in some of the stages of the forming process according to the said variant embodiment of the invention. With reference to Fig. 1, a panel for the inner facing of the passenger compartment of motor vehicles, particularly, for example, for the roof or the like consists of two thin sheets 1, 2 of what is known as Wood-Stock, in other words thermoplastic material, for example polypropylene filled with wood flour, or similar. One sheet 1 of Wood-Stock is substantially flat or shaped with a substantially continuous development of its surface. The other sheet 2 is shaped so that it has a plurality of indentations 102 on the outer side, extending towards the associated sheet 1, such that the surface 202 of the base side of the said indentations 102 inside the panel come into contact with it, and the two inner sides of the two sheets 1 and 2 are fixed together at the said surfaces 202. The indentations 102 are of any shape and are distributed in any way over the surface of the panel, the sheet 2 being shaped in such a way that the contact areas 202 are surrounded completely by an area in which the sheets 1 and 2 are spaced apart to form a cavity 3. Also, all of the cavities 3 associated with the areas of contact between sheets 1 and 2 communicate with each other. Both the sheets 1 and 2 have on their outer sides a finishing covering which consists of a thin sheet 4. The finishing sheet 4 may consist of any material, such as fabric, non-woven fabric, simulated leather, or similar. Preferably, the finishing sheet 4 consists of a non-woven fabric, with a weight from 20 g/m 2 to 500 g/m 2 and comprising polyester, viscose, polypropylene, nylon, and cotton mixture. Advantageously but not necessarily, the finishing sheet 4 is applied to the sheets of Wood-Stock before the fabrication of the panel, particularly at the stage of rolling of the sheet of Wood-Stock, so that at the time of fabrication of the panel the sheets of Wood-Stock are formed together with the attached finishing sheet. The depth of the cavities 3 may vary from a minimum of 2 to a maximum of 50 mm, according to the applications for which the panel is intended. Where the panel is used to form inner facings of vehicles, particularly the roofs of motor vehicles, sheets of Wood-Stock with a thickness preferably between 5 and 7 mm are used. Figs. 2 to 4 show a first example of a process of fabrication of the panel according to the invention. The two sheets of thermoplastic material 1, 2, namely Wood-Stock, with the finishing sheets 4 applied to the opposite sides, are unwound from two reels 6 and are fed simultaneously into a heating oven 7, in which heating lamps 8 are provided between the opposing non-covered sides of the sheets 1, 2. The two heated sheets 1, 2 are then fed between two press parts 9, 10 of the forming station. As is clearly shown in the sections in Figs. 3 and 4, one of the two press parts 9, 10, or both, in particular in the example the lower press part 10, have projections 11 projecting towards the opposing part, in this case the upper part 9, the said projections 11 being surrounded by intercommunicating depressions. In the example illustrated, the upper press part 9 is substantially smooth or shaped in a form corresponding to the visible shape of the panel. One or more positions for one or more corresponding blowing nozzles 12 are provided between the two press parts 9, 10, at one point at least of their outer edge and in an area communicating with the depressions among the projections 11. The nozzle may consist of a sleeve or similar which can be interposed between the two sheets 1, 2 disposed between the two press parts 9, 10. When the two press parts 9, 10 are closed against each other, and preferably as soon as the final closed position is reached, pressurized air, optionally treated (heated, dehumidified or humidified) is introduced through the blowing nozzle 12 between the two sheets 1, 2 disposed between the two press parts 9, 10. The areas corresponding to the depressions between the projections 11 of the lower press part 10 are therefore filled under pressure, while the two sheets 1, 2 are made to adhere completely to the profiles of the corresponding press parts 9, 10. The two sheets are then joined together at the upper surfaces of the projections 11 of the lower press part, between which and the coincident surface of the upper press part 9 the facing sides of the sheets 1, 2 are pressed against each other. In the areas of the depressions, however, the two sheets 1, 2 are detached from each other, forming the network of intercommunicating cavities 3. Figs. 5 to 9 show a forming press for the fabrication of the panels according to a variant of the process described previously, with which it is possible to form panels with cavities divided into areas which do not communicate with each other. With reference to Fig. 5, means 13 of pressing the outer edges of the two sheets of Wood-Stock 1, 2 are associated with each corresponding side of the lower part 10 of the press. The said means consist, in particular, of supporting plates 14 hinged to the corresponding side of the lower press part 10 so that they can be turned against it about an axis parallel to the associated side. Fixed to the free ends of the plates 14 are pressing fillets 15 which project beyond the plates so that they come down upon the outer edges of the sheets 1, 2 disposed on the lower press part, thus clamping the said edges together and against the flat outer edge of the lower press part 10. The pressing fillets 15 may be made of felt, teflon, or similar. Their pressing surface may advantageously be inclined to form a wedge, so that it progressively engages and compresses the outer edges of the sheets 1, 2. The associated ends of the pressing fillets 15 are made with complementary shapes, for example inclined at 45°, so that they come down upon the sheets 1, 2 in the corner areas also. The sheet 2 is initially disposed on the lower press part 10. The blowing nozzle or nozzles 12 are then inserted at predetermined points on the outer edge of the sheet, and the sheet 1 is laid on the sheet 2. The plates 14 are then swung upwards, as illustrated in Figs. 7 and 8, in which terminal upper position the associated pressing fillets 15 come down upon the outer edges of the sheets 1, 2, thus clamping them together. A cushion of air is generated through the blowing nozzle or nozzles 12 between the two sheets 1, 2, and the press is closed, as a result of which the compression of the two sheets 1, 2 against each other compresses the cushion of air and consequently pushes the sheet 2 into the depressions of the lower press part.

Claims: Panel of plastic material, consisting of two sheets (1, 2) of thermoplastic material, like polypropylene, filled with wood flour or similar, known as Wood-Stock, the two sheets (1, 2) having delimited areas of mutual contact (202) which are distributed in any way, are of any shapes and sizes, and are surrounded at least partially by cavity areas (3) in which the said two sheets (1, 2) are separate from each other; the cavity areas (3) may or may not communicate with each other, and the thickness of each of the two sheets (1, 2) is from 0.3 to 1.2 mm. Panel according to Claim 1, characterized in that each sheet of thermoplastic material (1, 2) has a thickness preferably from 0.5 to 0.6 mm. Panel according to Claim 1 or 2, characterized in that the outer side of the sheet (1) on the visible face of the panel, and optionally also the outer side of the sheet (2) on the rear face of the panel, may be covered with a finishing sheet (4), such as a cloth, a fabric, a non-woven fabric, simulated leather, adhesive papers. Panel according to Claim 3, characterized in that the finishing sheet (4) consists of polyester, viscose, polypropylene, nylon, cotton mixture, PVC, melamine material. Panel according to one or more of the preceding claims, characterized in that at least one finishing sheet (4) consists of a non-woven fabric with a weight from 20 g/m 2 to 500 g/m 2 . Panel according to one or more of the preceding claims, characterized in that at least the finishing sheet (4) on the side which is applied to a supporting structure consists of an adhesive melamine paper. Panel according to one or more of the preceding claims, characterized in that at least one of the sheets (1, 2) of thermoplastic material is substantially flat, or is shaped in a form complementary to the surface to which it is to be applied or adapted, or has a substantially continuous development according to the shape required by the client, while the other (1, 2) is further shaped so that it has a plurality of indentations (102) in the areas of contact (202) with the first sheet (1), and the sheet (2) provided with indentations (102) may form the visible face or the rear face of the panel, as necessary. Panel according to one or more of the preceding claims, characterized in that both sheets (1, 2) of thermoplastic material may have a plurality of indentations (102) forming the areas of mutual contact (202). Panel according to one or more of the preceding claims, characterized in that the depth of the cavities (3) is between 2 and 50 mm. Panel according to one or more of the preceding claims, characterized in that it is used for the internal facing of vehicles or similar and the cavities have a depth of 5 to 7 mm. Process for the fabrication of the panel according to one or more of the preceding claims, comprising the following stages: heating the sheets (1, 2) of thermoplastic material; feeding a first lower sheet (2) to the lower part (10) of a press; inserting at least one or more blowing nozzles (12) so that they are disposed above the outer edge of the lower sheet (2) of thermoplastic material; disposing a second sheet (1) over the first lower sheet (2) so that the second sheet is disposed over the end of the blowing nozzle or nozzles (12); partially compressing the two superimposed sheets (1, 2) of thermoplastic material against each other along their outer edges, to provide a substantially hermetic joint between the sheets along the said edges; generating a cushion of air between the two superimposed sheets (1, 2) of thermoplastic material by blowing air between them by means of the blowing nozzle or nozzles (12); closing the upper press part (9) against the lower press part (10). Process according to Claim 11, characterized in that the finishing sheets (4) may be applied to the sheets (1, 2) of thermoplastic material at a stage preceding their forming, in particular during the stage of extrusion of the sheets (1, 2) of thermoplastic material, or at a stage following the forming stage. Process according to Claim 11 or 12, characterized in that the blowing air may be treated, for example heated, humidified or dehumidified. Device for the fabrication of the panel according to one or more of the preceding Claims 1 to 10, and for the application of the process as claimed in Claims 11 to 13, comprising a station (7, 8) for heating the sheets (1, 2) of thermoplastic material followed by a forming station with a forming press consisting of two parts, an upper part (9) and a lower part (10), at least one (10) of which has projections (11) surrounded at least partially by depressions, while preferably the lower press part (10) has removable means (13) for mutual compression of the outer edges of the sheets of thermoplastic material (1, 2). Device according to Claim 14, characterized in that the removable means (13) for compression of the outer edges of the sheets (1, 2) of thermoplastic material consist of peripheral jaws for clamping the said outer edges against the outer edge of the lower press part (10). Device according to Claim 15, characterized in that the removable means (13) of compression consist of wedge-shaped or substantially wedge-shaped pressing fillets (15), whose lengths correspond to the lengths of each side of the lower press part (10), and which are carried by plates (14) hinged to the corresponding side of the lower press part (10) so that they can be turned about an axis parallel to the corresponding side of the lower press part (10). Device according to Claim 16, characterized in that the ends of the pressing fillets (15) associated with the corner areas of the sheets (1, 2) of thermoplastic material are made to be complementary to each other and to fit together, being, for example, inclined at 45° in the manner of a frame. Device according to one or more of the preceding claims, characterized in that the pressing fillets (15) consist of a felt or a teflon fillet.

Inventors: ODINO ADRIANO, VENERE GIORGIO, ODINO, ADRIANO, VENERE, GIORGIO
Applicants: GOR APPLIC SPECIALI SRL, G.O.R. APPLICAZIONI SPECIALI S.P.A.
Application year: 1994
Main classification: B44C5
IPC codes: B29C51, E04C2, B44C5, B29C49, B32B3, B32B27